From the time of the ancient world, at least, plants have been classified in two ways. On the one hand there is the detached academic, philosophical or scientific interest in plants themselves: this groups plants by their relationship to one another according to their similarities and differences in structure and function. Then there is the practical, utilitarian or anthropocentric interest which groups plants according to their human use. Cultivated plant taxonomy is concerned with the special classification categories needed for the plants of agriculture, horticulture and forestry as regulated by the Cultivated Plant Code. This Code serves not only the scientific interests of formal nomenclature, it also caters for the special utilitarian needs of people dealing with the plants of commerce. Those cultigens given names governed by the Cultivated Plant Code fulfill three criteria: they have special features considered of sufficient importance to warrant a name; the special features are the result of deliberate human breeding or selection and are not found in wild populations (except in rare cases where the special features represent desirable part of natural variation found in wild populations that is not covered by a scientific name); it is possible to perpetuate the desirable features by propagation in cultivation.